SCPI Commands in Python for Test Engineers

pip install pyvisa pyvisa-py

import pyvisa

rm = pyvisa.ResourceManager("@py")  # Pure Python backend
dmm = rm.open_resource("TCPIP::192.168.1.100::INSTR")
dmm.timeout = 5000  # 5 seconds

# Every SCPI instrument responds to *IDN?
idn = dmm.query("*IDN?")
print(f"Connected: {idn.strip()}")

dmm.write("*RST")
dmm.write("*CLS")

# DC voltage, auto-range
voltage = float(dmm.query(":MEAS:VOLT:DC?"))

# DC current, auto-range
current = float(dmm.query(":MEAS:CURR:DC?"))

# Resistance, auto-range
resistance = float(dmm.query(":MEAS:RES?"))

# AC voltage
ac_voltage = float(dmm.query(":MEAS:VOLT:AC?"))

# Configure for DC voltage, 10V range
dmm.write(":CONF:VOLT:DC 10")

# Trigger a measurement
dmm.write(":INIT")

# Wait for completion
dmm.query("*OPC?")

# Read the result
voltage = float(dmm.query(":FETCH?"))

import pyvisa
import time

rm = pyvisa.ResourceManager("@py")
psu = rm.open_resource("TCPIP::192.168.1.101::INSTR")
psu.timeout = 5000

psu.write("*RST")
psu.write("*CLS")

# Select channel and configure
psu.write(":INST:SEL CH1")
psu.write(":VOLT 5.0")          # Set 5V output
psu.write(":CURR 0.5")          # 500mA current limit

# Enable output
psu.write(":OUTP ON")
time.sleep(0.5)                  # Wait for stabilization

# Read actual values
actual_v = float(psu.query(":MEAS:VOLT?"))
actual_i = float(psu.query(":MEAS:CURR?"))
print(f"Output: {actual_v:.3f}V, {actual_i:.4f}A")

# Always disable output at the end
psu.write(":OUTP OFF")
psu.close()

# Basic oscilloscope setup
scope = rm.open_resource("TCPIP::192.168.1.102::INSTR")
scope.timeout = 10000

scope.write("*RST")
scope.write(":CHAN1:DISP ON")           # Enable channel 1
scope.write(":CHAN1:SCAL 1.0")          # 1V/div
scope.write(":TIM:SCAL 0.001")         # 1ms/div
scope.write(":TRIG:EDGE:SOUR CHAN1")    # Trigger on channel 1
scope.write(":TRIG:EDGE:LEV 1.5")      # Trigger at 1.5V

# Measure frequency and amplitude
frequency = float(scope.query(":MEAS:FREQ? CHAN1"))
amplitude = float(scope.query(":MEAS:VAMP? CHAN1"))

def check_errors(instr) -> list[str]:
    """Read all errors from the SCPI error queue."""
    errors = []
    while True:
        err = instr.query(":SYST:ERR?").strip()
        code = int(err.split(",")[0])
        if code == 0:
            break
        errors.append(err)
    return errors


# After a sequence of commands
errors = check_errors(dmm)
if errors:
    for e in errors:
        print(f"  Error: {e}")
    raise RuntimeError(f"Instrument errors: {errors}")

dmm.write(":CONF:VOLT:DC 10")       # Configure range
dmm.write(":TRIG:SOUR BUS")         # Bus trigger mode
dmm.write(":INIT")                   # Arm the trigger system
# ... do other setup ...
dmm.write("*TRG")                   # Send the trigger
dmm.query("*OPC?")                  # Wait for completion
reading = float(dmm.query(":FETCH?"))

import pyvisa
import openhtf as htf
from openhtf.plugs import BasePlug
from openhtf.util import units
from tofupilot.openhtf import TofuPilot


class ScpiDmm(BasePlug):
    """SCPI multimeter plug with automatic lifecycle."""

    RESOURCE = "TCPIP::192.168.1.100::INSTR"

    def setUp(self):
        rm = pyvisa.ResourceManager("@py")
        self.instr = rm.open_resource(self.RESOURCE)
        self.instr.timeout = 5000
        self.instr.write("*RST")
        self.instr.write("*CLS")

    def measure_dc_voltage(self, range_v: str = "AUTO") -> float:
        self.instr.write(f":CONF:VOLT:DC {range_v}")
        return float(self.instr.query(":MEAS:VOLT:DC?"))

    def measure_dc_current(self, range_a: str = "AUTO") -> float:
        self.instr.write(f":CONF:CURR:DC {range_a}")
        return float(self.instr.query(":MEAS:CURR:DC?"))

    def measure_resistance(self, range_ohm: str = "AUTO") -> float:
        self.instr.write(f":CONF:RES {range_ohm}")
        return float(self.instr.query(":MEAS:RES?"))

    def tearDown(self):
        self.instr.close()


@htf.measures(
    htf.Measurement("voltage_3v3")
    .in_range(3.2, 3.4)
    .with_units(units.VOLT),
)
@htf.plug(dmm=ScpiDmm)
def test_rail(test, dmm):
    test.measurements.voltage_3v3 = dmm.measure_dc_voltage()


def main():
    test = htf.Test(test_rail, procedure_id="FCT-001", part_number="PCBA-100")
    with TofuPilot(test):
        test.execute(test_start=lambda: input("Serial: "))